1. Field of the Invention
This invention relates to weight balancing mechanisms for a stand supporting an operation microscope.
2. Description of the Related Art
An operation microscope stand is known as a structure in which a main parallel linkage is rotatably supported on a rotation axis provided on a stand body which is installed on the floor or the ceiling; an operation microscope is supported via a supplemental parallel linkage at a distal end of a support arm which is an extension of the upper link of the main parallel linkage; and a counterweight is supported at an extension of the lower link of the first parallel linkage.
This operation microscope stand allows the main parallel linkage to be held at a desired position by bringing the mass center of the main parallel linkage and all the structures it supports in agreement with the rotation axis, using the counterweight for weight balancing on the rotation axis.
The operation microscope held at the distal end of the support arm via the supplemental parallel linkage can also be held at different angles by inclining the supplemental parallel linkage, for example.
This kind of operation microscope stand includes a weight balancing switch generally provided on an operating panel located at the stand body. After fitting the operation microscope and accessories to the supplemental parallel linkage, an operator presses the weight balancing switch provided on the operating panel. A weight balancing operation about the rotation axis for the main parallel linkage and a weight balancing operation for the operation microscope held by the supplemental parallel linkage are started for weight equilibrium of the main parallel linkage and the supplemental parallel linkage.
As a result, the operation microscope is held in the air as if it is floating in a zero-gravity space. Its weight equilibrium being attained in every direction, the operation microscope is kept at a desired position to which it has been moved or rotated.
In this related art, however, since both the weight balancing operation for the main parallel linkage and the weight balancing operation for the supplemental parallel linkage are performed by pressing the weight balancing switch provided on the operating panel, an operator, when he or she only wants to correct a slightly unbalanced state of the supplemental parallel linkage in a short period of time during surgery, has to perform an overall weight balancing operation, resulting in a complicated operation. More specifically, when an operator, during surgery, moves a part of the operation microscope supported by the supplemental parallel linkage relative to a supported part of the operation microscope, the form (the distribution of mass) of the operation microscope changes and its mass center shifts. Thus, the full weight equilibrium of the supplemental parallel linkage is disrupted. In this case also, an overall weight balancing operation is performed, taking time in adjustment, and preventing a prompt procedure.